®
L6911B
5 BIT PROGRAMMABLE POWER SUPPLY
CONTROLLER FOR PENTIUM II PROCESSOR
OPERATING SUPPLY VOLTAGE FROM 5V
TO 12V
TTL-COMPATIBLE 5BIT PROGRAMMABLE
OUTPUT FROM:
-1.3V TO 2.05V WITH 0.05V BINARY STEPS
-2.1V TO 3.5V WITH 0.1V BINARY STEPS
VOLTAGE MODE PWM CONTROL
EXCELLENT OUTPUT ACCURACY +/-1%
OVERLINE, AND TEMPERATURE VARIATIONS
HIGH PRECISION INTERNAL REFERENCE
DIGITALLY TRIMMED
VERY FAST LOAD TRANSIENT 0% TO 100%
DUTY CYCLE
POWER GOOD OUTPUT
OVERVOLTAGE PROTECTION
OVERCURRENT PROTECTION REALISED
USING THE MOSFET’s R
DSon
OPERATING FREQUENCY FROM 50KHz TO
1MHz
MEETS INTEL PENTIUM II SPECIFICATION
DISABLE FUNCTION
APPLICATION CIRCUIT
Vin 5V/12V
V
CC
5V/12V
SO20
Applications
POWER SUPPLY FOR ADVANCED MICRO-
PROCESSOR SUPPLIES
POWER SUPPLY FOR PENTIUM II INTEL
PROCESSORS
DESCRIPTION
The L6911B is a power supply controller specifi-
cally designed to provide a high performance
DC/DC conversion for Pentium II Microproces-
sors. A precise 5 bit digital to analog converter
OCSET
18
2
15
14
BOOT
UGATE
Vo
1.3V to 3.5V
13
17
16
11
1
PHASE
LGATE
PGND
GND
VSEN
VFB
VCC
OSC
OVP
VD0
VD1
VD2
VD3
VD4
SS
20
19
4
5
6
7
8
3
10
PGOOD
12
9
COMP
D98IN956B
April 1999
1/7
L6911B
DESCRIPTION
(continued)
(DAC) allows to adjust the output voltage from
1.3V to 2.05V with 0.05V binary steps and from
2.1V to 3.5V with 0.1V binary steps. The high pre-
cision internal reference, digitally trimmed, as-
sures the selected output voltage to within +/-1%.
Thanks to the window comparator system, the de-
vice provides excellent load transient perform-
ance. The high peak current gate drive affords to
ABSOLUTE MAXIMUM RATINGS
Symbol
V
CC
V
BOOT
-V
PHASE
V
CC
to PGND
Boot Voltage
Input, Output or I/O Voltage
Parameter
Value
15
15
-0.3 to V
CC
+0.3
Unit
V
V
V
have fast switching to the external power mos,
performing an high efficiency. The L6911B as-
sures a fast protection against load overvoltage
and load overcurrent. An external SCR is trig-
gered to crowbar the input supply in case of over-
voltage. In case of output short circuit the soft
start capacitor is discharged and the system
works in hiccup mode.
BLOCK DIAGRAM
V
CC
12V
Vin 5V
PGOOD
SS
VCC
OCSET
BOOT
MONITOR and
PROTECTION
OVP
RT
UGATE
OSC
PHASE
LGATE
PGND
Vo
1.8V to 3.5V
VD0
VD1
VD2
VD3
VD4
D/A
+
-
E/A
-
+
PWM
GND
VSEN
VFB
D98IN957A
COMP
THERMAL DATA
Symbol
R
thj-amb
T
max
T
stg
Parameter
Thermal Resistance Junction to Ambient
Maximum Junction Temperature
Storage Temperature Range
Value
110
150
-65 to 150
Unit
°C/W
°C
°C
RECOMMENDED OPERATING CONDITION
Symbol
V
CC
T
amb
T
J
V
CC
to PGND
Ambient Temperature Range
Junction Temperature Range
Parameter
Value
5V
±
10%/12V
±
10%
0 to 70
0 to 125
Unit
V
°C
°C
2/7
L6911B
PIN CONNECTION
VSEN
OCSET
SS
VID0
VID1
VID2
VID3
VID4
COMP
FB
1
2
3
4
5
6
7
8
9
10
D98IN958
20
19
18
17
16
15
14
13
12
11
RT
OVP
VCC
LGATE
PGND
BOOT
UGATE
PHASE
PGOOD
GND
PIN FUNCTIONS
N°
1
2
Name
VSEN
OCSET
Description
Connected to the output voltage is able to manage overvoltage conditions and the PGOOD
signal.
A resistor connected from this pin and the upper Mos Drain sets the current limit protection.
The internal 200
µ
A current generator sinks a current from the drain through the external
resistor. The overcurrent threshold is due to the following equation:
I
P
=
3
SS
I
ocs
⋅
R
ocs
Rdson
The soft start time is programmed connecting an external capacitor from this pin and GND.
The internal current generator forces through the capacitor 10µA. This pin can be used to
disable the device forcing a voltage lower than 0.4V.
Voltage Identification code pins. These input are open collector and TTL compatible. Are used
to program the output voltage as specified in Table 1 and to set the overvoltage and
powergood thresholds.
This pin is connected to the error amplifier output and is used to compensate the voltage
control feedback loop.
This pin is connected to the error amplifier inverting input and is used to compensate the
voltage control feedback loop.
All internal voltage reference are referred to this pin.
This pin is an open collector output and is pulled low if the output voltage is not within
±
10%
of the programmed voltage. This pin is forced high if the ”11111” VID is set.
This pin is connected to the source of the upper mosfet and provides the return path for the
high side driver. This pin monitors the drop across the upper mosfet for the current limit.
High side gate driver output.
Bootstrap capacitor pin. Through this pin is supplied the high side driver and the upper mosfet.
Power ground pin. This pin has to be connected closely to the low side mosfet source in order
to reduce the noise injection into the device.
This pin is the lower mosfet gate driver output.
Device supply voltage. The operative supply voltage range is 4.5V to 12V.
Do not connect V
IN
to 12V if V
CC
is 5V.
Over voltage protection. If the output voltage reach the 15% above the programmed voltage
this pin is driven high and can be used to drive an external SCR that crowbar the supply
voltage.
3/7
4-8
VID0 - 4
9
10
11
12
13
14
15
16
17
18
19
COMP
FB
GND
PGOOD
PHASE
UGATE
BOOT
PGND
LGATE
VCC
OVP
L6911B
PIN FUNCTION
(continued)
N°
20
Name
RT
Description
Oscillator Switching frequency pin. Connecting an external resistor from this pin to ground the
switching frequency is increased according to the equation:
R
T
(
K
Ω)
Connecting the resistor from this pin and the Vcc the Switching frequency is reduced
according to the equation:
R
T
(KΩ)
If the pin is not connected the switching frequency is 200kHz.
f
S
=
200kHz
−
f
S
=
200kHz
+
5
⋅
10
6
4
⋅
10
7
ELECTRICAL CHARACTERISTICS
Symbol
I
CC
POWER-ON
Rising V
CC
Threshold
Falling V
CC
Threshold
Rising VOCSET Threshold
OSCILLATOR
Free Running Frequency
Total Variation
∆
V
osc
Ramp Amplitude
DACOUT voltage Accuracy
ERROR
AMPLIFIER
DC Gain
GBW
SR
I
UGATE
R
UGATE
I
LGATE
R
LGATE
Gain-Bandwidth Product
Slew Rate
Upper Gate Source
Upper Gate Sink
Lower Gate Source
Lower Gate Sink
Overvoltage Trip
(V
SEN
/DACOUT)
I
OCSET
I
OVP
I
SS
4/7
OCSET Current Source
OVP Sourcing Current
Soft Start Current
V
OCSET
= 4.5VDC
V
SEN
= 5.5V, V
OVP
= 0V
COMP = 10pF
V
BOOT
- Vphase = 12V,
V
UGATE
= 6V
I
LGATE
= 0.3A
V
CC
= 12V, V
LGATE
= 6V
I
LGATE
= 0.3A
-
-
-
0.6
-
1.2
-
-
170
60
10
88
15
10
1
1.5
2
1
115
200
-
-
-
-
3
-
2
120
230
dB
MHz
V/
µ
s
A
Ω
A
Ω
%
µ
A
mA
µA
RT = open
R
T
to GND >6k
Ω
,
R
T
to V
CC
= 12V > 200kΩ
RT = open
VID0, VID1, VID2, VID3 see
Table1
185
-15
-
-1
200
-
1.9
-
215
15
-
1
kHz
%
V
%
VOCSET = 4.5V
VOCSET = 4.5V
-
3.6
-
-
-
1.26
4.6
-
-
V
V
V
Parameter
Supply current
Test Condition
UGATE and LGATE open
Min.
-
Typ.
5
Max.
-
Unit
mA
VCC SUPPLY CURRENT
REFERENCE and DAC
GATE DRIVERS
PROTECTION
L6911B
ELECTRICAL CHARACTERISTICS
(continued)
Symbol
Parameter
Upper Threshold
(V
SEN
/DACOUT)
Upper Threshold
(V
SEN
/DACOUT)
Hysteresis
(V
SEN
/DACOUT)
V
PGOOD
PGOOD Voltage Low
Test Condition
V
SEN
Rising
V
SEN
Rising
Upper and Lower Threshold
I
PGOOD
= -5mA
Min.
106
89
-
-
Typ.
-
-
2
0.5
Max.
111
94
-
-
Unit
%
%
%
V
Table 1.
VID4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
VID3
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
VID2
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
VID1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
VID0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
OUTPUT VOLTAGE (V)
1.3
1.35
1.4
1.45
1.5
1.55
1.6
1.65
1.7
1.75
1.8
1.85
1.9
1.95
2
2.05
0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3
3.1
3.2
3.3
3.4
3.5
5/7
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